# Chi-squared estimate of homogeneity of diagnosticity ratio Function for getting chi-squared value for homogeneity of diagnosticity ratios ```r chi_diag(df) ``` ## Arguments - `df`: A dataframe containing: ln(d), variance of ln(d), d weights ## Returns Chi squared estimate of homogeneity of diagnosticity ratios for k independent lineups ## Details * To compute linedf, use the diag_param helper function. * To compute df, apply ln_diag_ratio, var_lnd & d_weights functions to linedf, then bind results into one dataframe (see Examples ) * The order in which the estimates are bound together (i.e., their position in the dataframe) is important, and should always be as follows: row 1: **var**, row 2: **lnd**, row 3: **wi**. ## Examples ```r #Target present data: A <- round(runif(100,1,6)) B <- round(runif(70,1,5)) C <- round(runif(20,1,4)) lineup_pres_list <- list(A, B, C) rm(A, B, C) #Target absent data: A <- round(runif(100,1,6)) B <- round(runif(70,1,5)) C <- round(runif(20,1,4)) lineup_abs_list <- list(A, B, C) rm(A, B, C) #Pos list lineup1_pos <- c(1, 2, 3, 4, 5, 6) lineup2_pos <- c(1, 2, 3, 4, 5) lineup3_pos <- c(1, 2, 3, 4) pos_list <- list(lineup1_pos, lineup2_pos, lineup3_pos) rm(lineup1_pos, lineup2_pos, lineup3_pos) #Nominal size: k <- c(6, 5, 4) #Use diag param helper function to get data (n11, n21, n12, n22): linedf <- diag_param(lineup_pres_list, lineup_abs_list, pos_list, k) #Get ln(d), variance of ln(d) & d weights: ratio <- ln_diag_ratio(linedf) var <- var_lnd(linedf) wi <- d_weights(linedf) #Bind estimates into one df of 3 rows & x observations #(see Details above) df <- t(cbind(ratio, var, wi)) #Call: chi_diag(df) ``` ## References Malpass, R. S. (1981). Effective size and defendant bias in eyewitness identification lineups. **Law and Human Behavior, 5**(4), 299-309. Malpass, R. S., Tredoux, C., & McQuiston-Surrett, D. (2007). Lineup construction and lineup fairness. In R. Lindsay, D. F. Ross, J. D. Read, & M. P. Toglia (Eds.), **Handbook of Eyewitness Psychology, Vol. 2: Memory for people** (pp. 155-178). Mahwah, NJ: Lawrence Erlbaum Associates. Tredoux, C. G. (1998). Statistical inference on measures of lineup fairness. **Law and Human Behavior, 22**(2), 217-237. Tredoux, C. (1999). Statistical considerations when determining measures of lineup size and lineup bias. **Applied Cognitive Psychology, 13**, S9-S26. Wells, G. L., Leippe, M. R., & Ostrom, T. M. (1979). Guidelines for empirically assessing the fairness of a lineup. **Law and Human Behavior, 3**(4), 285-293.

chi_diag function